Contact structure and semiconductor device

ABSTRACT

To improve the reliability of contact with an anisotropic conductive film in a semiconductor device such as a liquid crystal display panel, a terminal portion ( 182 ) of a connecting wiring ( 183 ) on an active matrix substrate is electrically connected to an FPC ( 191 ) by an anisotropic conductive film ( 195 ). The connecting wiring ( 183 ) is manufactured in the same process with a source/drain wiring of a TFT on the active matrix substrate, and is made of a lamination film of a metallic film and a transparent conductive film. In the connecting portion with the anisotropic conductive film ( 195 ), a side surface of the connecting wiring ( 183 ) is covered with a protecting film ( 173 ) made of an insulating material. Accordingly, the portion in which the metallic film is surrounded by the transparent conductive film, the insulating base film, and the protecting film ( 173 ) to which it is in contact with, can be avoided from exposure to air because the side surface of the metallic film of the connecting wiring is covered with the protecting film ( 173 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device comprising acircuit structured with a thin film transistor (hereinafter referred toas TFT) formed on a substrate having an insulating surface, and alsorelates to a structure of a terminal for connecting the circuitstructured with the TFT to a circuit on another substrate. Moreparticularly, the present invention provides a technique suitable foruse in a liquid crystal display device having a pixel portion and adriver circuit provided in the periphery of the pixel portion on thesame substrate, an electro-luminescence display device, and electronicequipment mounted with an electro-optical device incorporating the abovedisplay devices. Note that in the present specification, thesemiconductor device indicates general devices that may function by useof semiconductor characteristics, and that not only the above liquidcrystal display device, but also the above electronic equipmentincorporating the display device are categorized as the semiconductordevice.

2. Description of the Related Art

In the electro-optical device, typically an active matrix type liquidcrystal display device, a technique in which a TFT is utilized for thepurpose of structuring a switching element and an active circuit hasbeen developed. A TFT is formed with a semiconductor film as an activelayer formed on a substrate such as a glass substrate by vapor phasegrowth. A material such as silicon or silicon germanium having siliconas its principal constituent is suitably utilized for the semiconductorfilm. In addition, an amorphous silicon film or a crystalline siliconfilm typically such as a polycrystalline silicon film can be obtaineddepending on the manufacturing method of the silicon semiconductor film.

The TFT using the amorphous silicon film as the active layer essentiallycannot attain an electric field effect mobility of several cm²/Vsec ormore because of electronic properties caused by the amorphous structure,or the hie. Accordingly, despite being able to utilize the TFT as theswitching element (pixel TFT) for driving the liquid crystals providedin each pixel in the pixel portion, it is impossible to form the TFT upto a point as a driver circuit for performing image display. In order toprovide a driver circuit for performing image display, a technique inwhich a driver IC is mounted by the TAB (rape Automated Bonding) methodor the COG (Chip On Glass) method has been employed.

On the other hand, with the TFT using the crystalline silicon film asthe active layer, it is possible to attain a high electric field effectmobility to form various functional circuits on the same glasssubstrate. Besides the pixel TFT, in the driver circuit, circuitsbasically formed of a CMOS circuit consisting of an n-channel TFT and ap-channel TFT, such as a shift resistor circuit, a level shiftercircuit, a buffer circuit, and a sampling circuit, can be manufacturedon the same substrate. An active matrix substrate having the pixel andthe driver circuit for driving the pixel formed on the same substrate isutilized in the active matrix type liquid crystal display device for thepurpose of reducing cost and improving quality.

In the active matrix substrate such as the above, in order to supplyelectric power and an input signal to the driver circuit, a connectingwiring connected to the driver circuit is formed on the active matrixsubstrate. A structure mounted with the connecting wiring and an FPC(Flexible Print Circuit) is being adopted. An anisotropic conductivefilm is used for the connection of the connecting wiring and the FPC onthe substrate. FIG. 30 shows a sectional structure of the connectingwiring connected to the FPC by means of the anisotropic conductive film.

As shown in FIG. 30, in the active matrix substrate, a connecting wiring3 is formed on an insulating film 2 that is on the surface of a glasssubstrate 1. The FPC 4 includes a substrate made of a flexible materialsuch as polyimide, and a plurality of wiring 6 made of copper etc. areformed thereon. In an anisotropic conductive film 7, conductive spacers8 are dispersed into an adhesive 9 (resin) that cures from heat orlight. The connecting wiring 3 is electrically connected to a wiring 6on the FPC 4 by a conductive spacer 8.

The connecting wiring 3 is a two multi-layer structure consisting of ametallic film 3 a such as aluminum and titanium and a transparentconductive film 3 b such as an ITO film. Since the transparentconductive film 3 b utilizes a metallic film such as aluminum, itswiring resistance can be lowered. Hence, there is fear that the metallicfilm 3 a may be deformed due to being pressed by a conductive spacer 8.The transparent conductive film 3 b is made of metal oxide such asindium and tin, thus its degree of hardness is higher than the metallicfilm 3 a. Accordingly, the transparent conductive film 3 b is formed onthe surface of the metallic film, preventing the metallic film 3 a frombeing damaged or deformed.

Nonetheless, a side surface of the metallic film 3 a is in an uncoveredstate, and exposed to air until an anisotropic conductive film 7 isformed. The metallic film 3 a is under a state easily exposed tocorrosion and oxidation, the cause of lowering the connectionreliability of the connecting wiring 3 and the FPC 4. Furthermore, theside surface of the metallic film 3 a is touching the resin in a statewhere the FPC 4 is mounted, causing a problem in protecting againstmoisture.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above-mentionedproblems, and therefore has an object thereof to realize a highreliability connection between an FPC and the connecting wiring, and toprovide a connecting wiring suitable for mass production.

In order to solve the above problems, according to one aspect of thepresent invention, there is provided a contact structure forelectrically connecting a connecting wiring on a substrate to a wiringon another substrate by means of an anisotropic conductive film,characterized in that the lead wiring is a lamination film formed of ametallic film and a transparent conductive film, and in a connectingportion with the anisotropic conductive film, a side surface of themetallic film is covered with a protecting film.

Further, according to another aspect of the present invention, there isprovided a semiconductor device having, on a substrate, a circuitstructured with a thin film transistor, and a connecting wiring forconnecting the circuit structured with the thin film transistor toanother circuit, characterized in that the connecting wiring is alamination film of a metallic film and a transparent conductive film,and in a connecting portion with the other circuit, a side surface ofthe metallic film is covered with a protecting film.

Further, according to another aspect of the present invention, there isprovided a semiconductor device comprising a first substrate having acircuit structured with a thin film transistor and a second substrateopposing the first substrate, characterized in that a connecting wiring,formed of a metallic film and a transparent conductive film in contactwith the metallic film surface for connecting the circuit structuredwith a thin film transistor to another circuit, and a protecting film incontact with a side surface of the metallic film, are formed on thefirst substrate.

Still further, according to another aspect of the present invention,there is provided a semiconductor device comprising a first substratehaving a circuit structured with a thin film transistor and a secondsubstrate opposing the first substrate, characterized in that aconnecting wiring formed of a metallic film and a transparent conductivefilm in contact with the metallic film surface, for connecting thecircuit structured with a thin film transistor to another circuit acolumn-shape spacer for maintaining a space between the first substrateand the second substrate, formed on the thin film transistor, and aprotecting film in contact with a side surface of the metallic filmformed of a same material as that of the column-shape spacer, are formedon the first substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are diagrams showing top views for explaining astructure of an active matrix substrate;

FIG. 2 is a block diagram for explaining a circuit structure of a liquidcrystal display device;

FIGS. 3A to 3D are sectional views showing a manufacturing process of anactive matrix substrate;

FIGS. 4A to 4D are sectional views showing a manufacturing process of anactive matrix substrate;

FIGS. 5A to 5C are sectional views showing a manufacturing process of anactive matrix substrate;

FIGS. 6A and 6B are sectional views showing a manufacturing process ofan active matrix substrate;

FIG. 7 is a sectional view showing a manufacturing process of an activematrix substrate;

FIG. 8 is a diagram showing the sectional view of a liquid crystalpanel;

FIGS. 9A to 9C are sectional views showing a manufacturing process of aterminal portion of a connecting wiring;

FIGS. 10A to 10C are sectional views showing a manufacturing process ofa terminal portion of a connecting wiring;

FIGS. 11A to 11C are sectional views showing a manufacturing process ofa terminal portion of a connecting wiring;

FIGS. 12A and 12B are sectional views showing a contact structure of aterminal portion of the connecting wiring and an anisotropic conductivefilm;

FIG. 13 is a diagram showing a top view of one pixel of a pixel portion;

FIG. 14 is a diagram for explaining a shape of a column-shape spacer;

FIGS. 15A to 15F are sectional views showing a manufacturing process ofa terminal portion of a connecting wiring;

FIG. 16 is a sectional view showing a contact structure of a terminalportion of the connecting wiring and an anisotropic conductive film;

FIGS. 17A to 17C are sectional views showing a manufacturing process ofan active matrix substrate;

FIGS. 18A to 18C are sectional views showing a manufacturing process ofan active matrix substrate;

FIGS. 19A to 19C are sectional views showing a manufacturing process ofan active matrix substrate;

FIG. 20 is a diagram showing a sectional view of a liquid crystal panel;

FIGS. 21A to 21F are sectional views showing a manufacturing process ofa terminal portion of a connecting wiring;

FIG. 22 is a diagram showing an example of a semiconductor device;

FIGS. 23A to 23F are diagrams showing examples of semiconductor devices;

FIGS. 24A to 24D are diagrams showing a structure of a projector typeliquid crystal display device;

FIG. 25 is a diagram showing a plasma producing mechanism of an ICPetching device;

FIG. 26 is a diagram showing an ICP etching device employing amulti-spiral coil method;

FIG. 27 is a diagram showing a dependency of a taper angle θ on biaspower;

FIG. 28 is a diagram showing a dependency of a taper angle θ on theratio of CF₄ flow;

FIG. 29 is a diagram showing a dependency of a taper angle θ on theselective ratio of tungsten to resist (W/resist); and

FIG. 30 is a diagram showing a conventional contact structure of aterminal portion of an active matrix substrate and an anisotropicconductive film.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment Mode 1

A contact structure according to the present invention is suitable for asemiconductor device that uses a mounting method in which circuits areconnected by means of an anisotropic conductive film, such as an activematrix type liquid crystal display device or an EL display device.Referring to FIGS. 12A and 12B, the contact structure of the presentinvention when applied to the active matrix type liquid crystal displaydevice is described in Embodiment Mode 1.

A connecting wiring 183 on an active matrix substrate is electricallyconnected to an FPC 191 by an anisotropic conductive film 195 in aterminal portion 182. The connecting wiring 183 is formed in the sameprocess in which a source/drain wiring of a on the active matrixsubstrate is formed. In other words, the connecting wiring 183 is formedfrom the same material and in the same layer as that of the source/drainwiring. The connecting wiring 183 is a lamination film of a metallicfilm 140 and a transparent conductive film 141. In a connecting portionwith the anisotropic conductive film 195, a side surface of theconnecting wiring 183 is covered with a protecting film 174.

A side surface of the metallic film 140 is covered with the protectingfilm 174 in this structure. Accordingly, in the connecting portion, themetallic film 140 is surrounded by and contacts with the transparentconductive film 141, an insulating film 109, and the protecting film174, with no chance of being exposed to air. Consequently, corrosion ofthe metallic film 140 can be prevented.

The protecting film 174 can be formed by using the insulating filmformed on the upper layer of the source/drain wiring. In Embodiment Mode1, the protecting film 174 is formed in the same process with acolumn-shape spacer 172 that is formed for the purpose of maintaining aspace between the active matrix substrate and an opposing substrate.

Furthermore, a connecting wiring 303 can be formed in the same processwith a gate wiring of the TFT as shown in FIG. 16. In this case, theconnecting wiring 303 is formed from the same material and in the samelayer as the gate wiring. Also in this case, a protecting film 304 isformed from insulating films 138 and 139 formed between the gate wiringand the source/drain wiring.

According to the present invention, the connecting wiring is formed of alamination film in which a transparent conductive film is formedcovering the surface of the metallic film. The metallic film is notlimited to a single layer film. The thickness of the metallic film isbetween 100 nm and 1 μm. The metallic film may be a metallic layerhaving an element selected from the group consisting of aluminum (Al),tantalum (Ta), Titanium (Ti), molybdenum (Mo), and tungsten (W) as itsprincipal constituent, or at least containing an alloy layer whichcontains a metallic element. The following may be given as the alloy:Mo—W alloy, Mo—Ta alloy, or nitrated compounds with the listed elementsabove such as tantalum nitride (TaN), tungsten nitride (WN), titaniumnitride (TD), and molybdenum nitride (MoN). In addition, a silicidelayer such as tungsten silicide, titanium silicide, and molybdenumsilicide may be included in the metallic film.

The thickness of the transparent conductive film is between 50 nm and 5mm. Materials such as indium oxide (In₂O₃), or an indium oxide/tin oxidealloy (In₂O₃—SnO₂:ITO) formed by utilizing the sputtering method and thevacuum evaporation method may be used as materials for the transparentconductive film. The etching treatment of this type of material isperformed with hydrochloric acid solutions. However, particularly theetching of ITO readily generates residues. Therefore, an indiumoxide/zinc oxide alloy (In₂O₃—ZnO) may be used in order to be suitablefor the etching process. The indium oxide/zinc oxide alloy has excellentflat and smooth surface properties, and contrary to ITO, also hasexcellent thermal stability. Accordingly, at an edge surface of a drainwiring 169 where it comes in contact with Al, corrosion reaction with Alcan be prevented. Similarly, zinc oxide (ZnO) is also a suitablematerial. In order to further improve the transmissivity of visiblelight and conductivity, zinc oxide doped with gallium (ZnO:G), etc. maybe used.

Embodiment Mode 2

Further, for the case of forming the connecting wiring in the sameprocess with the gate wiring, the shape of the sectional surfaces of thegate wiring and the connecting wiring can be taper shapes. By formingthe gating wiring into a taper shape, film thickness is reduce from thecenter towards the side surface. Because of this variation in filmthickness, as shown in an embodiment which will be explained later,changing an impurity concentration to be doped into the semiconductorfilm can be made by utilizing the variation in film thickness in aprocess of doping for the semiconductor film with the gate wiring as amask.

Dry etching utilizing high-density plasma is applied in order to form ataper shaped gate wiring. As a means of achieving high-density plasma,an etching device that utilizes a microwave or an ICP (InductivelyCoupled Plasma) is suitable. Particularly, the ICP etching device caneasily control plasma as well as deal with the operation of processingfor a large area surface substrate.

As a means for performing plasma treatment with high precision, a plasmatreatment device utilizing the ICP employs a method of forming plasma byapplying high frequency electric power to a multi-spiral coil formedfrom 4 whirlpool shaped coil parts connected in series via an impedancematching apparatus. The length of each whirlpool shaped coil parts isset to be ¼ times longer than the wavelength of the high frequency. Inaddition, the plasma treatment device is structured such that adifferent high frequency electric power is also applied to a baseelectrode for holding the object to be treated to thereby add a biasvoltage. The plasma treatment method utilizing an ICP and plasmatreatment device are disclosed in Japanese Patent Application Laid-openNo. Hei 9-293600.

FIG. 25 schematically shows the structure of the plasma treatment deviceutilizing such type of ICP (for example, an etching device). On a quartzsubstrate 11 of a chamber's top portion, an antenna coil 12 is arranged,and connected to an RF electric power source 14 via a matching-box 13.Furthermore, a substrate 10 to be plasma treated is disposed on a baseelectrode 15 which is provided facing the antenna coil. The baseelectrode 15 is also connected to an RF electric power source 17 via amatching box 16. When an RF electric current flow is applied to theantenna coil 12 above substrate, an RF electric current J flows in an adirection in the antenna coil 12 to thereby generate a magnetic field Bin a Z direction in accordance with a formula 1.μ_(o) J=rotB (μ_(o) is permeability)  (Formula 1)Then, complying with the law of electromagnetic induction of Faraday, aninduction electric field E occurs in the θ direction.−∂B/∂t=rotE  (Formula 2)

Plasma is produced when an electron is accelerated in the α direction tothereby collide with a gas molecule in the induction electric field E.Since the direction of the induction electric field E is in the αdirection, the probability of losing electric charge due to collision ofa charged particle against the wall of the etching chamber or thesubstrate is reduced. Accordingly, high-density plasma can be generatedeven at a low pressure of about 1 Pa. Also, there is hardly any magneticfield B in the downward flow, resulting in a high-density plasma regionthat has widened into a sheet shape.

In order to obtain the high-density plasma with the ICP, it is necessaryto flow a high frequency electric current J at a low-loss, which flowsto the antenna coil 12, and its impedance must be reduced for the largearea. Therefore, it is effective to apply a method in which the antennacoil is split.

Regulating the respective RF powers to be applied to the antenna coil 12(applied with an ICP power) and the lower electrode 15 of the substrateside (applied with bias power) makes it possible to independentlycontrol the plasma density and the self-bias voltage. Additionally, anRF power with different frequencies may be applied in response to thefilm to be etched.

To obtain the high-density plasma with the ICP etching device, the RFelectric current J that flows to the antenna coil 12 needs to be flowedat a low-loss. The inductance of the antenna coil 12 must be reduced inorder to form a large surface area of the substrate. As shown in FIG.26, an ICP etching device having a multi-spiral coil 22 of a splitantenna has been developed to achieve the above stated conditions. InFIG. 26, reference numeral 21 denotes a quartz substrate, referencenumerals 23 and 26 denote matching-boxes, and reference numerals 24 and27 denote RF electric power sources. Further, at the bottom portion ofthe chamber, a base electrode 25 for holding a substrate 28 is providedvia an insulator 29.

If the etching device, which uses the ICP and is applied with themulti-spiral coil, is employed, then the etching of the heat-resistantconductive materials can be performed well and in addition, a wiringwith a desirable taper angle θ may be formed.

A bias power density of the ICP etching device is adjusted to therebyobtain a desired taper angle θ. FIG. 27 is a view showing the bias powerdependency of the taper angle θ. As shown in FIG. 27, the taper angle θcan be controlled in response to the bias power density. Shown in FIG.27 is the result of examining the taper shape (taper angle) of thepatterned edge portion of a W film, which has been formed into a fixedpattern on the glass substrate. FIG. 28 shows the bias power (13.56 MHz)dependency of the taper angle and the bias power is applied to thesubstrate side. As common conditions, the electric discharge power (highfrequency power to be applied to the coil, 1336 MHz) is set to 3.2W/cm², the pressure is set to 1.0 Pa, and CF₄ and Cl₂ are used as theetching gas. The quantity of flow of the etching gas CF₄ and Cl₂, areboth set to 30 SCCM.

As shown in FIG. 27, it has become apparent that when the bias power isin the range of 128 to 384 mW/cm², the taper angle may be alteredbetween 70° and 20°. Note that the quantity of flow of CF₄ and Cl₂ areboth set to 30 SCCM.

It is also possible to alter the taper angle from 60° to 80° as can beknown from the experiment shown in FIG. 28. The experiment conditions ofFIG. 28 show the results of examining the dependency of the taper angleon the ratio of the quantity of flow of etching gas. Note that thequantity of flow of CF₄ is altered in a range of from 20 to 40 SCCM withthe condition that the total quantity of flow of CF₄ and Cl₂ is set to60 SCCM. The bias power at this point is set to 128 mW/cm².

Further, it is deemed that the taper angle θ depends on the selectivityof the etching of tungsten and resist. FIG. 29 is a diagram showing thedependency of the taper angle θ on the selective ratio of tungsten andresist. Using the ICP etching device in such a way, when the bias powerdensity and the ratio of the quantity of flow of reaction gas areappropriately determined, it is possible to very easily form a wiringwith a desired taper angle θ of between 3° and 60°.

In addition, the processing characteristics of the ICP etching devicefor the heat-resistant conductive materials is taken into consideration.Besides a W film and a Ta film, regarding a molybdenum-tungsten (Mo—W)alloy (composition ratio is Mo:W=48:50 wt %) that is often used as thematerial for the gate electrode, a typical value of an etching speed, anapplicable etching gas, and a selective ratio to a gate insulating filmthat becomes the base of the gate electrode are shown here. The gateinsulating film is a silicon oxide film or a silicon nitride oxide filmformed with plasma CVD. The selective ratio here is defined as the ratioof the etching speed of the gate insulating film to the etching speed ofeach material.

TABLE 1 Selective ratio Etching speed with the gate Material (nm/min)insulating film CF₄ + Cl₂ Ta 140-160   6-8 Cl₂ Mo-W 40-60 0.1-2 CF₄ +Cl₂

The etching speed of the Ta film is between 140 and 160 nm/rain, and theselective ratio of etching to the gate insulating film is between 6 and8. This value surpasses the value of the selective ratio between 2 and 4of the W film to the gate insulating film when the etching speed of theW film in the range of 70 to 90 nm/min. Therefore, the Ta film is alsoapplicable from the viewpoint of the characteristic of the workability.Although not shown in the table, the resistivity of the Ta film isbetween 20 and 30 μΩcm, compared with the resistivity of the W filmwhich is between 10 and 16 μΩcm, the Ta film resistivity is relativelyhigher and resulting into a difficult point.

On the other hand, the etching speed of the Mo—W alloy is slow andbetween 40 and 60 nm/min, its selective ratio of etching to the gateinsulating film is between 0.1 and 2. It can be seen from the viewpointof the characteristic of the workability that this material is notnecessarily applicable. As can be known from table 1, the Ta film showsthe best results. However, as stated above, when the resistivity istaken into consideration, then it is deemed that the W film is suitableafter considering all the factors.

Further, as the etching gas for dry etching, mixed gas of gas containingfluorine and gas containing chlorine may be used. Gas selected from CF₄,C₂F₆, and C₄F₈ may be used as the gas containing fluorine, and gasselected from Cl₂Cl₂, SiCl₄, and BCl₄ may be used as the gas containingchlorine.

Embodiment 1

This Embodiment relates to an active matrix type liquid crystal panel.FIG. 1A is a diagram showing the top view of the active matrix substrateof this Embodiment in which a pixel portion and a driver circuit fordriving the thin film transistor of the pixel portion are formedthereon, and also shows the positional relationship between acolumn-shape spacer formed on the active matrix substrate and a sealingagent.

As shown in FIG. 1A, on a glass substrate 101, there are provided apixel portion 188 disposed with a thin film transistor, a scanningsignal driver circuit 185, and an image signal driver circuit 186 a asthe driver circuit for driving the thin film transistor disposed in thepixel portion. In addition, a signal processing circuit 187 such as CPUor a memory circuit is provided.

In the pixel portion 188, a gate wiring 189 extending from the scanningsignal driver circuit 185 and a source wiring 190 extending from theimage signal driver circuit 186 a intersect into a matrix shape to formpixels. Each pixel is provided with a pixel TFT 204 and a storagecapacitor 205 as shown in FIG. 6A.

A column-shape spacer 172, a cylindrical structured object made ofresin, is for maintaining a space between the active matrix substrateand an opposing substrate. The column-shape spacer 172 to be provided inthe pixel portion 188 may be provided not only to each pixel, but alsoto every several pixels or several tens of the pixels arranged in amatrix shape. In other words, the ratio of the total number of pixelscomposing the pixel portion to the number of spacers is good between 20%and 100%. In addition, driver circuits 185 to 187 may be provided withresin covering the entire surface of the circuits, instead of thecolumn-shape spacer 172. The cylindrical spacer is provided inaccordance with the position of the source wiring and the drain wiringof the TFT in this embodiment.

On the substrate 101, the sealing agent 186 is formed on the exterior ofthe pixel portion 188, the scanning signal driver circuit 185, the imagesignal driver circuit 186, and the signal processing circuit 187 of theother circuits, and on the interior of an external input/output terminal182.

The driver circuits 185 to 187 on the active matrix substrate 101 areelectrically connected to an external power source or an externalcircuit by the connecting wiring 183. The connecting wiring 183 isformed at the same time with the source (drain) wiring of the TFT of thedriver circuits 185 to 187. The terminal portion 182 is integrallyformed with the connecting wiring 183, and becomes a connecting portionwith the wiring on the other substrate. FIG. 1B shows the partialenlarged view of the terminal portion 182.

As shown in FIG. 1B, the side surface of the terminal portion 182 iscovered with a protecting film 173. The connecting wiring 183 in theterminal portion 182 is electrically connected to a wiring 191 b of theFPC 191 by the anisotropic conductive film. The reference numeral 191 adenotes the substrate that is provided with the FPC 191.

FIG. 2 is a block diagram showing the circuit of the active matrixsubstrate 101. The image signal driver circuit 186 is composed of ashift resistor circuit 501; a level shifter circuit 502 a, a buffercircuit 503 a, and a sampling circuit 504. In addition, the scanningsignal driver circuit 185 is composed of a shift resistor circuit 501 b,a level shifter circuit 502 b, and a buffer circuit 503 b.

The driving voltages of the shift resistor circuits 501 a and 501 b arebetween 5 and 16V (typically 10V). A CMOS circuit forming this circuitis formed of a first p-channel TFT 200 and a first n-channel TFT 201 asshown in FIG. 6. Though the driving voltage of the level shiftercircuits 502 a and 502 b and the buffer circuits 503 a and 503 b becomehigher, between 14 and 16V, a TFT identical with that of the shiftresistor may be used. Moreover, it is effective to form the gates inthese circuits into a multi-gate structure to thereby raisepressure-resistance and improve reliability.

The sampling circuit 504 is formed from an analog switch and its drivingvoltage is between 14 to 16V. Since the polarity alternately reverses tobe driven and there is a necessity to reduce an off current value, it isdesired that the sampling circuit 504 be formed of a second p-channelTFT 202 and a second n-channel TFT 203 as shown in FIG. 6. When the offcurrent value of the p-channel TFT 202 becomes a problem, a single drainstructured TFT provided with an offset region formed in a process thatwill be shown in Embodiment 2, may be used to form this circuit.

Further, the driving voltage of the pixel portion is between 14 and 16V. From a viewpoint of reducing power consumption, there is a demand tofurther reduce the off current value of the pixel portion than that ofthe sampling circuit. Accordingly, it is desired that the pixel portionbe a multi-gate structure as a pixel TFT 204 shown in FIG. 6, andadditionally be a structure provided with an LDD region.

Note that only the block structures of the pixel portion 188 and thedriver circuits 185 and 186 have been shown. Other circuits such as asignal distributing circuit, a frequency dividing circuit, a D/Aconverter, a γ-correction circuit, an op-amp circuit, and further signalprocessing circuits 187 such as a memory circuit and an arithmeticoperation circuit, and still further a logical circuit, may all beformed on the same substrate in accordance with the process of the TFTwhich will be explained later. According to the present invention, asemiconductor device having the pixel portion and the driver circuitsformed on the same substrate, for example, a liquid crystal displaydevice provided with the signal driver circuit and the pixel portion canbe realized.

Hereinafter, a process of manufacturing an active matrix substrate willbe explained. FIGS. 3A to 7 are sectional views showing themanufacturing process of the pixel portion 188 and the driver circuits.FIGS. 9A to 11C are diagrams showing a manufacturing process of theterminal portion 182 of the connecting wiring 183. The same referencenumerals in these diagrams denote the same constituents.

A barium borosilicate glass or aluminoborosilicate glass as typified byCorning #7059 glass and #1737 glass can be used for a substrate 101.Besides these glass substrates, plastic substrates not having opticalanisotropy such as polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyethersulfone (PES), etc, can be used, too. In thecase of using a glass substrate, the substrate may be heat-treated inadvance at a temperature lower by about 10 to 20° C. than a glass strainpoint. A base film 102 comprising such as a silicon oxide film, asilicon nitride film or a silicon oxynitride film is formed over thesurface of the substrate 101, on which TFT is to be formed, in order toprevent the diffusion of impurities from the substrate 101. For example,a laminate of the silicon oxynitride film 102 a formed from SiH₄, NH₃and N₂O by plasma CVD to a thickness of 10 to 200 nm (preferably, 50 to100 nm) and a hydrogenated silicon oxide nitride film 102 b formedsimilarly from SiH₄, NH₃ and N₂O to a thickness of 50 to 200 nm(preferably, 100 to 150 nm), is formed. (FIG. 3A)

The silicon oxynitride film is formed by using the conventional parallelplate type plasma-enhanced CVD. The silicon oxynitride film 102 a isformed by introducing SiH₄ at 10 sccm, NH₃ at 100 sccm and N₂O at 20sccm into a reaction chamber under the condition of a substratetemperature of 325° C., a reaction pressure of 40 Pa, a discharge powerdensity of 0.41 W/cm² and a discharge frequency of 60 MHz. These filmscan be formed by only changing the substrate temperature and byswitching the reactive gases.

The silicon oxynitride film 102 a thus formed has a density of9.28×10²²/cm³, has a slow etching rate of about 63 nm/min in a mixedsolution (“LAL500”, a product of Stella Chemifa. Co.) containing 7.13%of ammonium hydrogenfluoride (NH₄HF₂) and 15.4% of ammonium fluoride(NH₄F) at 20° C., and is a compact and hard film. When such a film isused for the base film, the diffusion of alkali metal elements from theglass substrate into the semiconductor layers formed thereon can beeffectively prevented.

Next, a semiconductor film 103 a having a thickness of 25 to 80 nm(preferably, 30 to 60 nm) and an amorphous structure is formed by aknown method such as plasma CVD or sputtering. For example, an amorphoussilicon film is formed to a thickness of 55 nm by plasma CVD.Semiconductor films having such an amorphous structure include anamorphous semiconductor film and a micro-crystalline semiconductor film,and a compound semiconductor film having an amorphous structure such asan amorphous silicon-germanium film may also be used. Both the base film102 and the amorphous semiconductor layer 103 a can be formedcontinuously. For example, after the silicon oxynitride film 102 a andthe hydrogenated silicon oxynitride film 102 b are formed continuouslyby the plasma CVD process as described above, the deposition can becarried out continuously by switching the reactive gases from Sa₄, N₂Oand H₂ to SiH₄ and H₂, or SiH₄ alone, without exposing to the atmosphereof the open air. As a result, the contamination of the surface of thehydrogenated silicon oxynitride film 102 b can be prevented, andvariance of the characteristics of the TFT to be fabricated andfluctuation of the threshold voltage can be reduced.

The crystallization step is then carried out to form a crystallinesemiconductor film 103 b from the amorphous semiconductor film 103 a. Alaser annealing method, a thermal annealing method (solid phase growthmethod) or a rapid thermal annealing method (RTA) method can be used forthis method. In the case of using the glass substrate or the plasticsubstrate having a low heat resistance, the laser annealing method isemployed preferably. The RTA method uses an IR lamp, a halogen lamp, ametal halide lamp or a xenon lamp as the light source. Alternatively,the crystalline semiconductor film 103 b can be formed by thecrystallization method using a catalytic element in accordance with thetechnology disclosed in Japanese Patent Application Laid-Open No. Hei7-130652. In the crystallization step, hydrogen contained in theamorphous semiconductor film is first discharged preferably. Afterheat-treatment is conducted at 400 to 500° C. for about 1 hour to lowerthe hydrogen content to 5 atom % or below, the crystallization step isthen conducted. In this way, roughness of the film surface can beprevented advantageously.

When the crystallization step is conducted by the laser annealingmethod, a pulse oscillation type or continuous light emission typeexcimer laser, or an argon laser is used as the light source. In thecase of using the pulse oscillation type excimer laser, the laser beamis processed to a linear shape and laser annealing is then conducted.The laser annealing condition may be selected appropriately by theoperator, for example, the laser pulse oscillation is set at 30 Hz andthe laser energy density is 100 to 500 mJ/cm² (typically, 300 to 400mJ/cm²). The linear beams are irradiated to the entire surface of thesubstrate, and the overlap ratio of the linear beams at this time is 80to 98%. In this way, the crystalline semiconductor film 103 b can beobtained as shown in FIG. 3B.

A resist pattern is formed on the crystalline semiconductor film 103 bby photolithography that uses a photo-mask PM1. The crystallinesemiconductor film is divided into islands by dry etching, formingthereby island semiconductor films 104 to 108. A mixed gas of CF₄ and O₂is used for dry etching.

An impurity imparting p-type may be added in a concentration of about1×10¹⁶ to 5×10¹⁷ atoms/cm³ to the entire surface of the islandsemiconductor films in order to control the threshold voltage (Vth) ofthe TFT. The elements of the Group XIII of the Periodic Table such asboron (B), aluminum (Al) or gallium (Ga) are known as the impurityelements for imparting p-type to the semiconductor. Ion implantation orion doping can be adopted as the method of doping these elements, bution doping is suitable for processing a substrate having a large area.This ion doping method uses diborane (B₂H₆) as a source gas and addsboron (B). Addition of such an impurity element is not always necessaryand may be omitted. However, this is the method that can be usedappropriately for keeping the threshold voltage of the n-channel TFT, inparticular, within a prescribed range.

A gate insulating film 109 is formed from an insulating film containingsilicon to a thickness of 40 to 150 nm by plasma CVD or sputtering. Forexample, it may be formed from a silicon oxynitride film having athickness of 120 nm. The silicon oxynitride film that is formed byadding O₂ to SiH₄ and N₂O has a reduced fixed charge density in the filmand is a preferable material for this application. Needless to say, thegate insulating film is not particularly limited to such a siliconoxynitride film but may be a single layered structure of otherinsulating film containing silicon or their laminate structure. (FIG.3C)

A conductive film is formed as shown in FIG. 3D to form a gate wiring onthe gate insulating film 109. The conductive film may comprise a singlelayer, but may be a laminate structure of plurality of layers such asdouble layer or triple layer, if necessary. For example, in the case itis a double layer structure, the upper film is formed from a metal filmcomprising an element selected from tantalum (Ta), titanium (Ti),molybdenum (Mo) and tungsten (W), etc. as the principle component oralloy films comprising these elements (typically, a Mo—W alloy film, anMo—Ta alloy film), and the lower film is formed from tantalum nitride(TaN), tungsten nitride (WN), titanium nitride (TiN), molybdenum nitride(MoN), etc. For example, in the case of double layer, the upper film maybe formed from a nitride of the conductive lower film, when it isdenoted like lower/upper, they may be WN film/W film or TaN film/Tafilm, or the like. In the case of a triple layer, it may be TaN film/Tafilm/TaN film. It is preferable to set the resistivity of the second(upper) conductive film within a range of 10 to 50 mWcm. The impurityconcentration contained may be preferably reduced for low resistance,specifically the oxygen concentration may be reduced to 30 ppm or below.For example, resistivity of 20 mWcm or below can be realized withrespect to tungsten (W) by setting the oxygen concentration at 30 ppm orbelow.

Further, it is preferable to use a film having aluminum as its principlecomponent for achieving low resistivity of the wiring. In this case, theheat resistance may be enhanced by adding trace amount of Si or Sc orthe hie into aluminum For example, as a conductive film which forms agate wiring, Ti film/Al film added with Sc or Ti film/TiN film/Al filmadded with Sc may be formed.

In the case of using W for the gate electrode, tungsten nitride (WN) isformed to a thickness of 50 nm for the conductive layer 111 bysputtering using W as a target and by introducing an argon (Ar) gas anda nitrogen (N₂) gas, and W is formed to a thickness of 250 nm for theconductive layer 110. As another method, W film can be formed by thermalCVD using tungsten hexafluoride (WF₆). In any case, the resistance ofthe gate electrode must be lowered, and the resistivity of the W film ispreferably not higher than 20 mWcm. The low resistivity of the W filmcan be accomplished by increasing the crystal grain size, but theresistivity becomes high when the contents of the impurity elements suchas O in W are great because crystallization is impeded. Therefore, whensputtering is employed, the W target used has a purity of 99.9999%, andsufficient attention should be paid lest impurities mix from the gaseousphase during the formation of the film. In this way, the resistivity of9 to 20 mWcm can be achieved.

It is possible to form TaN film and Ta film similarly by sputtering. Toform the TaN film, Ta is used as the target and a mixed gas of Ar andnitrogen, as the sputtering gas. Argon (Ar) is used as the sputteringgas to form the Ta film. When a suitable amount of Xe or Kr is added tothe sputtering gas, the internal stress of the resulting films can bemitigated and peel of the films can be prevented. The resistivity of thea phase Ta film is about 20 mWcm, and this film can be used for the gateelectrode. However, the resistivity of the β phase Ta film is about 180mWcm and this film is not suitable for the gate electrode. The TaN filmhas a crystal structure approximate to that of the α phase. Therefore,when the Ta film is formed on the TaN film, the α phase Ta film can beobtained easily. In the present Embodiment, TaN film is deposited as thelower conductive film 110, and Ta, as the upper conductive film 111,which form the gate wiring.

Incidentally, it is effective to form a phosphorus (P) doped siliconfilm to a thickness of about 2 to about 20 nm between the conductivefilm which forms the gate wiring and the gate insulating film 109. Bydoing so, the improvement of adhesiveness and prevention of oxidation ofthe conductive film formed thereon can be devised and at the same timeit is possible to prevent the alkali metal elements contained in theconductive film in a trace amount to diffuse into the gate insulatingfilm 109.

Next, resist masks RM1 to RM6 are formed by photolithography by using aphoto-mask PM2. The conductive layer 110 and the conductive layer 111are collectively etched to form gate electrodes 118 to 122 and acapacitance wiring 123. These gate electrodes 118 to 122 and capacitancewiring 123 comprise a unitary structure of 118 a to 122 a formed of aconductive film and 118 b to 123 b formed of a conductive film. (FIG.4A)

To form an LDD region in the n-channel 1, a doping step of an impurityelement for imparting the n type (n⁻ doping step) is conducted. Here,the impurity element imparting n-type is doped by ion-doping byself-alignment with the gate electrodes 118 to 122 as the mask.Phosphorus (P) is doped as the impurity element imparting n-type withinthe range of 1×10¹⁶ to 5×10¹⁹ atoms/cm³. In this way, the lowconcentration n-type impurity regions 124 to 129 are formed in theisland-like semiconductor films as shown in FIG. 4B.

Next, formation of high concentration n-type impurity region thatfunctions as a source or a drain region in the n-channel TFT, isconducted (n⁺ doping step). First, resist masks RM8 to RM12 are formedusing a photo-mask PM3, and an impurity element imparting n-type isdoped to form high concentration n-type impurity regions 130 to 135.Phosphorus (P) is used as the impurity element imparting n-type. Iondoping using phosphine (PH₃) is employed so that the concentration fallswithin the range of 1×10²⁰ to 1×10²¹ atoms/cm³ (FIG. 4C).

High concentration p-type impurity regions 136 and 137 are formed as thesource and drain regions in the island-like semiconductor films 104 and106 forming the p-channel TFT. Here, an impurity element impartingp-type is doped with the gate electrodes 118 and 120 as the mask, andthe high concentration p-type impurity regions are formed byself-alignment.

At this time, resist masks RM13 to RM15 are formed on the island-likesemiconductor films 105, 107 and 108 forming the n-channel TFTs by usinga photo-mask PM4 to cover the entire surface. High concentration p-typeimpurity regions 136 and 137 are formed by ion doping that uses diborane(B₂H₆). The boron (B) concentration in the regions is 3×10²⁰ to 3×10²¹atoms/cm³ (FIG. 4D).

Phosphorus (P) is added to the high concentration p-type impurityregions 136 and 137 in a preceding step, in a concentration of 1×10²⁰ to1×10²¹ atoms/cm³ with respect to the high concentration p-type impurityregions 136 a and 137 a, and in a concentration of 1×10¹⁶ to 5×10¹⁹atoms/cm³ with respect to the high concentration p-type impurity regions136 b and 137 b. However, by setting the concentration of boron (B)added in this step to become 1.5 to 3 times higher, no trouble occurs inthe function as the source and drain regions of the p-channel TFT.

Thereafter, as shown in FIG. 5A, a protective insulating film 138 isformed from above the gate wiring and the gate insulating film. Theprotective insulating film 138 may comprise a silicon oxide film, asilicon oxynitride film, a silicon nitride film or a laminate filmcomprising the combination of these films In any case, the protectiveinsulating film 138 is formed of an inorganic insulating material. Theprotective insulating film 138 has a film thickness of 100 to 200 nm.When the silicon oxide film is used, tetraethyl orthosilicate (TEOS) andO₂ are mixed, and the film can be formed by plasma CVD with a reactionpressure of 40 Pa, a substrate temperature of 300 to 400° C. and plasmais discharged at a high frequency (1356 MHz) power density of 0.5 to 0.8W/cm².

When the silicon oxynitride film is used, the film may comprise asilicon oxynitride film formed by plasma CVD from SiH₄, N₂O and NH₃ or asilicon oxynitride film formed from SiH₄ and N₂O. The film depositioncondition in this case is the reaction pressure of 20 to 200 Pa, thesubstrate temperature of 300 to 400° C., and the high frequency (60 MHz)power density of 0.1 to 1.0 W/cm². The hydrogenated silicon oxynitridefilm formed from SiH₄, N₂O and H₂ may be used, as well. The siliconnitride film can be formed similarly from SiH₄ and NH₃ by plasma CVD.

Thereafter, the step of activating the impurity elements impartingn-type or p-type added in the respective concentrations is conducted.This step is conducted by a thermal annealing method using a furnaceannealing oven. Besides the thermal annealing method, it is possible toemploy a laser annealing method and a rapid thermal annealing method(RTA method). The thermal annealing method is conducted in a nitrogenatmosphere containing oxygen in a concentration of 1 ppm or below,preferably 0.1 ppm or below, at 400 to 700° C., typically 500 to 600° C.In this embodiment, the heat-treatment is conducted at 550° C. for 4hours. When a plastic substrate having a low heat-resistant temperatureis used for the substrate 101, the laser annealing method is preferablyemployed (FIG. 5B).

After the activation step, heat-treatment is further conducted in anatmosphere containing 3 to 100% hydrogen at 300 to 450° C. for 1 to 12hours to hydrogenate the island-like semiconductor film. This is theprocess step that terminates the dangling bonds of 10¹⁶ to 10¹⁸/cm³ inthe island-like semiconductor film by hydrogen that is thermallyexcited. Plasma hydrogenation (using hydrogen that is excited by plasma)may be used as another means for hydrogenation.

After the activation and hydrogenation steps are completed, aninterlayer insulating film 139 made of an organic insulating material isformed to a mean thickness of 1.0 to 2.0 mm. Examples of the organicresin materials are polyimide, acrylic, polyimide, polyimidamide, BCS(benzocyclobutene), and so forth. When polyimide of the type, that isthermally polymerized after being applied to the substrate, is used, thematerial is baked at 300° C. in a clean oven. When acrylic is used, atwo-component type is used. After the main agent and the curing agentare mixed, the mixture is applied to the entire surface of the substrateby using a spinner. Preparatory heating is then conducted by using a hotplate at 80° C. for 60 seconds, and baking is then made in the cleanoven at 250° C. for 60 minutes. (FIG. 5C)

By forming the interlayer insulating film 139 from an organic insulatingmaterial, its surface can be planarized satisfactorily. The organicresin materials have generally a low dielectric constant, and theparasitic capacitance can be reduced. However, since they arehygroscopic, they are not suitable for the protective film. Therefore,the organic insulating material must be used in combination with thesilicon oxide film, the silicon oxynitride film or the silicon nitridefilm formed as the protective insulating film 138 as in this embodiment.

Thereafter, a resist mask having a predetermined pattern is formed byusing a photomask PM5 (FIG. 6A). Contact holes reaching the source ordrain regions of the respective island-like semiconductor films areformed in the insulating films 138 and 139. Further, insulating films138 and 139 are removed from the terminal section 182. The contact holesare formed by dry etching. In this case, a mixed gas of CF₄, O₂ and Heis used as the etching gas. The interlayer insulating film 139 formed ofthe organic resin material is first etched. Then, the etching gas isswitched to CF₄ and O₂, and the protective insulating film 138 isetched. To improve the selection ratio with the island-likesemiconductor films, the etching gas is switched further to CHF₃ and thegate insulating film is etched. In this way, the contact holes can beformed satisfactorily.

A laminate film of a metal film 140 which forms a source/drain wiringand connection wiring 183 and a transparent conductive film 141 isformed. Here Ti film is formed to a thickness of 50 to 150 nm as themetal film 140, which is brought to form contact with the semiconductorfilm that form the source region or the drain region, and aluminum (Al)is formed into a thickness of 300 to 400 nm by sputtering to overlap theTi film. Further; a laminate film comprising Ti film/TiN film/Al filmmay be formed as the metal film 140.

The material of transparent conductive film can be formed from indiumoxide (In₂O₃) or an alloy of indium oxide and tin oxide (In₂O₃—SnO₂;ITO) by sputtering or vacuum evaporation. The etching treatment of thesematerials is performed by solution including hydrochloric acid. However,since residues are easily generated specifically in the etching of ITO,the alloy of indium oxide and zinc oxide (In₂O₃—ZnO₂) may be used inorder to improve etching workability. The alloy of indium oxide and zincoxide has superiority in the surface smoothness and in thermal stabilitycompared to ITO, and it can prevent corrosion reaction with Al whichwill be in contact at the edge surface of the drain wiring 169.Similarly zinc oxide (ZnO) is also an appropriate material, and a zincoxide added with gallium (ZnO:Ga) for the purpose of increasingtransmittivity of visible rays and conductivity or the like can also beused. In the present embodiment alloy of indium oxide and zinc oxide isformed as the transparent conductive film 141.

FIGS. 9A to 9C show the structure in the terminal section 182 ofconnection wiring 183 which corresponds to FIG. 6A. FIG. 9A correspondsto a cross section vertical to the longitude direction of the wiring,FIG. 9B corresponds to a cross direction along the longitude directionand they are made to clearly show structure with respect to the TFT andthe laminate relations. FIG. 9C is a top view. FIGS. 10A to 11C aresimilar to these.

A resist mask pattern is then formed by using a photo-mask PM6. Sourcewirings 148 to 152 and drain wirings 153 to 158 are formed by etching,and connection wiring 183 is formed as shown in FIG. 10. Here, the drainwiring 157 functions as the pixel electrode. (FIGS. 6B and 10A to 10C)

When the hydrogenation treatment is conducted under this state,favorable results can be obtained for the improvement of TFTperformance. For example, the heat-treatment may be conducted preferablyat 300 to 450° C. for 1 to 12 hours in an atmosphere containing 3 to100% of hydrogen. A similar effect can be obtained by using the plasmahydrogenation method. Such a heat-treatment can diffuse hydrogenexisting in the protective insulating film 138 and the base film 102into the island-like semiconductor films 104 to 108 and can hydrogenatethese films In any case, the defect density in the island-likesemiconductor films 104 to 108 is lowered preferably to 10¹⁶/cm³ orbelow, and for this purpose, hydrogen may be added in an amount of about0.01 to about 0.1 atomic %.

When the six photo-masks are used as described above, a substrate havingthe TFTs of the driving circuit and the pixel TFTs of the pixel portionover the same substrate can be completed. The first p-channel TFT 200,the first n-channel TFT 201, the second p-channel TFT 202 and the secondn-channel TFT 203 are formed in the driving circuit. The pixel TFT 204and the storage capacitance 205 are formed in the pixel portion. In thisspecification, such a substrate will be referred to as an “active matrixsubstrate” for convenience sake.

The first p-channel TFT 200 in the driving circuit has a single drainstructure that comprises in the island-like semiconductor film 104: thechannel formation region 206; and the source regions 207 a and 207 b andthe drain regions 208 a and 208 b each comprising the high concentrationp-type impurity region.

In the island-like semiconductor film 105 of the first n-channel TFT201, there are formed: the channel formation region 209; the LDD region210 that does not overlap with the gate electrode 119; the source region212; and the drain region 211. The length of this LDD region 210 in thedirection of the channel length is 1.0 to 4.0 mm, preferably 2.0 to 3.0mm. As the length of the LDD region in the n-channel TFT is determinedin this way, a high electric field occurring in the proximity of thedrain region can be mitigated, and the occurrence of hot carriers anddegradation of the TFT can be prevented.

The second p-channel TFT 202 of the sampling circuit has the singledrain structure in which the channel formation region 213, the sourceregions 214 a and 214 b and the drain regions 215 a and 215 b comprisingthe high concentration p-type impurity region are formed in theisland-like semiconductor film 106.

A channel formation region 216, LDD regions 217 and 218, a source region220 and a drain region 219 are formed in the island semiconductor film107 of the second n-channel TFT 203. The length of the LDD regions 217and 218 is set at between 1.0 and 4.0 mm.

The channel forming regions 221 and 222, LDD regions 223 to 225, sourceor drain regions 226 to 228 are formed in the island-lib: semiconductorfilm 108 of the pixel a 204. The length of the LDD region in thedirection of the channel length is 0.5 to 4.0 min, preferably 1.5 to 2.5mm. Furthermore, a storage capacitor is connected to the pixel TFT 204.The storage capacitance 205 is a capacitance which has the gateinsulating film 209 as a dielectric, and capacitance wiring 123 and thesemiconductor film 229 which is connected to the drain region 228 of thepixel TFT 204 as the electrodes. In FIG. 6B, the pixel TFT 204 is adouble gate structure. However, it may have a single gate structure or amulti-gate structure having a plurality of gate electrodes.

FIG. 13 is a top view showing almost one pixel of the pixel portion. Thecross section A-A′ in the drawing corresponds to the sectional view ofthe pixel portion shown in FIG. 6B. The gate electrode 122 of the pixelTFT 204, that functions also the gate wiring, crosses the island-likesemiconductor film 108 below it through a gate insulating film, notshown in the drawing. The source region, the drain region and the LDDregion are formed in the island-like semiconductor film 108, though theyare not shown in the drawing. Reference numeral 256 denotes a contactportion between the source wiring 152 and the source region 226.Reference numeral 257 denotes a contact portion between the drain wiring157 and the drain region 228. A storage capacitance 205 is formed by theoverlapping region of the semiconductor layer 229 that extends from thedrain region 228 of the pixel lei 204 and a capacitance wiring 123through the gate insulating film. In this construction, an impurityelement for valency control is not added to the semiconductor layer 229.

The construction described above makes it possible to optimize thestructure of the TFT constituting each circuit in accordance with thespecification required by the pixel TFT and the driving circuit, and toimprove operation performance and reliability of the semiconductordevice. Furthermore, this construction makes it easy to activate the LDDregion, the source region and the drain region by forming the gateelectrode by a conductive material having heat resistance.

Further in this embodiment columnar spacer 172 is formed, as shown inFIG. 7, on the active matrix substrate which went through the abovedescribed processes. At the same time, a protection film 174 whichprotects side face of the terminal section 182 of the connection wiring183 is formed with the formation of the columnar spacer 172. Thematerial of the columnar spacer 172 is not limited, in particular, andthey may be formed by using, for example, “NN700” of JSR Co., and afterthe material is coated by a spinner, a prescribed pattern is formed byexposure and development. The pattern is then heated and cured at 150 to200° C. in a clean oven, or the like.

The shape of the spacer thus formed can be changed depending on theconditions of exposure and development. Preferably, however, thecolumnar spacer 172 has a columnar shape with a flat top as shown inFIG. 14, so that the mechanical strength as the liquid crystal displaypanel can be secured when the substrate on the opposite side is put. Theshape is not particularly limited and may be conical or pyramidal. Whenit is conical, for example, the height H is 1.2 to 5 mm, the mean radiusL1 is 5 to 7 mm and the ratio of the mean radius L1 to the radius L2 ofthe bottom is 1:1.5. The taper angle of the side surface is not greaterthan ±15° at this time.

The arrangement of the columnar spacer may be decided arbitrarily.Preferably, however, the columnar spacer 172 is disposed in such amanner as to be superposed with, and cover, the contact section 251 ofthe drain wiring 157 (pixel electrode) in the pixel section 188 as shownin FIG. 7. Since planarity at the contact section 251 is lost and theliquid crystal is not oriented well at this section, disclination, etc.can be prevented by forming the columnar spacer 172 in the form in whichthe spacer resin is filled to the contact section.

The protection film 174 which protects the side face of the connectionwiring 183 is formed in the manufacturing process of the columnar spacer172, as shown in FIG. 11. The protection film 174 is formed so as toexpose only the surface of the transparent conductive film 141 in theterminal portion 182. The shape of the protection film 174 can bedetermined by the conditions of the exposure and development treatmentAccording to this structure, because the metal film 140 is in contactand covered with the protection film 174, gate insulating film 109 andtransparent conductive film 141, it will not be exposed to open air.

Thereafter, the alignment film 173 is formed on the surface of thesubstrate 101. The alignment film 173 is not formed at the terminalsection 182. A polyimide resin is used generally for the alignment filmof the liquid crystal display element After the alignment film isformed, rubbing treatment is conducted so that the liquid crystalmolecules are oriented with a certain pre-tilt angle. The region fromthe end portion of the columnar spacer 172 disposed in the pixel sectionto the region that is not rubbed, in the rubbing direction is notgreater than 2 mm. The occurrence of static electricity often becomesthe problem during the rubbing treatment. When the spacer 172 is formedover the TFT of the driving circuit, too, both original role as thespacer and the protection effect of the TFT from static electricity canbe acquired.

Thus an active matrix substrate in which the columnar spacer 172 whichholds the distance between the substrates and the substrate 101 areintegrated, is completed. Note that the structure can be made to formthe columnar spacer 172 after forming the alignment film 173. (FIGS. 7and 11 a to 11 c)

A shielding film 252, a color filter not shown in the drawing, atransparent conductive film 253 and an alignment film 254 are formedover the substrate 251 as shown in FIG. 8, for the substrate which willbe in pair with the active matrix substrate. Ti, Cr, Al and the hie isformed to a thickness of 150 to 300 nm for the shielding film 252.

The active matrix substrate formed with the pixel section and the drivercircuit as shown in FIG. 8 and the opposing substrate are then stucktogether by the sealant 179. A filler is mixed into the sealant 179, andthe two substrates are stuck together by holding a uniform distance bythis filler and the columnar spacer 172. A liquid crystal material 260is then injected in the clearance of the substrates, completely sealedby the sealant (not shown) and the liquid crystal panel is complete.

Further, in order to connect the circuits over the active matrixsubstrate 100 to the circuit for inputting image signal and the powersupply for supplying electric power, or the like, the connection wiring183 and the FPC 191 are electrically connected by anisotropic conductivefilm 195 in the terminal section 182, as shown in FIG. 12. FIG. 12A is across sectional view of the plane vertical to the longitude direction ofthe wiring of the terminal section 182 and FIG. 12B is a cross sectionalong the longitude direction.

As shown in FIGS. 12A and 12B, the anisotropic conductive film 195comprises a grain 195 b of several dozens to several hundreds mm platedwith gold, chromium or the like, in the adhesive 195 a. The activematrix substrate 100 and the FPC 191 can be electrically connected whenthe grain 195 b contacts the connection wiring 183 and the wiring of theFPC 191 b. In order to increase adhesive strength between the FPC 191and the substrate 109, the FPC 191 is placed outside the externalterminal section 182, resin layer 192 is disposed at the edge portion,and the mechanical strength is increased.

Embodiment 2

The connecting wiring 183 is formed in the same manufacturing processwith a source/drain wiring of the TFT in Embodiment 1. In Embodiment 2,the connecting wiring 183 will be formed in the same process with a gatewiring. Embodiment 2 will be explained with reference to FIG. 15. Themanufacturing process of the TFT will be employed from Embodiment 1. Thereference numerals in FIG. 15 which are identical with those of FIGS. 3Ato 8 denote the same constituents.

First the manufacturing processes until FIG. 9C are performed inaccordance with those of Embodiment 1. Next, a lamination film of aconductive film 301 and a transparent conductive film 302 composing thegate wiring, are formed. The material for forming conductive films 110and 111 composing the gate wiring in Embodiment 1 can be used for theconductive film 301. As for the transparent conductive film 302, thematerial used for forming the transparent conductive film 141 that isformed on the surface of the source/drain wiring of the TFT; can beutilized. As the conductive film 301, a lamination film made of a WNfilm/W film is formed by sputtering, and as the transparent conductivefilm 302, an ITO film is formed. (See FIG. 15A)

A resist mask is then formed as shown in FIG. 4A. Etching is performedon the conductive film 301 and the transparent conductive film 302, thenthe gate wiring of the TFT and a connecting wiring 303 as shown in FIG.15B are formed. In the case the films are formed from a materialincluding W as its principal constituent, it is desired that dry etchingusing high-density plasma be applied in order to implement a speedy andprecise etching.

As one means of achieving high-density plasma, it is appropriate toemploy the ICP (Inductively Coupled Plasma) etching device. In theetching method of W employing the ICP etching device two types of gas,CF₄ and Cl₂ are introduced into the reaction chamber for the etchinggas, the pressure is set between 0.5 and 1.5 Pa (preferably 1 Pa), and a200 W to 1000 W high frequency (1356 MHz) electric power is applied tothe inductively coupled portion. At this point, a 20 W high frequencyelectric power is applied to a stage disposed with the substrate, and bycharging a negative electric potential by self-bias, a positive ion isaccelerated to thereby perform anisotropic etching. By using the ICPetching device, an etching speed of between 2 and 5 nm/sec can also beattained from hard metallic films such as W. Further, in order toperform etching without leaving any residues, it is appropriate toincrease the etching time about 10% to 20% to perform over-etching.

However, attention must be paid to the selective ratio of etching to abase film. For example, the selective ratio of the W film to the siliconnitride oxide film (the gate insulating film 109) is between 2.5 to 3.Due to this type of over-etching process, an exposed surface of thesilicon nitride oxide film is etched between 20 and 50 nm, becomingsubstantially thinner.

As explained in Embodiment 1, the semiconductor film of the TFT is thendoped with phosphorous and boron to thereby form a protecting insulatingfilm 138 as shown in FIG. 5A. Then the phosphorous and boron doped intothe semiconductor film is activated. (See FIG. 15C)

Thereafter, an interlayer insulating film 139 is formed as shown in FIG.5C. The material for forming the interlayer insulating film 139 may beselected from the materials described in Embodiment 1, or the interlayerinsulating film 139 may be a silicon base inorganic insulating film, oran organic resin film such as acrylic. (See FIG. 15D)

As shown in FIG. 6, a contact hole reaching the source region or thedrain region, formed on an island-like semiconductor film, is formed inthe protecting insulating film 138 and the interlayer insulating film139. At the same time, in the terminal portion of the connecting wiring303, a protecting film 304 for covering the side surface of the terminalportion is formed. (See FIG. 15 e)

The rest of the processes are carried out in the same way as inEmbodiment 1 to thereby complete the active matrix substrate 100. Thenthe active matrix substrate 100 and an opposing substrate 250 are sealedtogether by a sealing agent 179 with a liquid crystal substance 260enclosed therein. The connecting wiring 303 and the FPC 191 areelectrically connected by the anisotropic conductive film 195. (See FIG.15F)

In Embodiment 2, because the side surface of the conductive film 301 ofthe connecting wiring 303 is covered with the protecting film 304, theconductive film 301 becomes a structure surrounded by the protectingfilm 304, the gate insulating film 109, and the transparent conductivefilm 302, and will not be exposed to air.

Embodiment 3

Embodiment 3 is a modified example of Embodiment 1 in which thesectional shape of a gate wiring is formed to be a taper shape. Further,it is also an example of forming the connecting wiring in the samemanufacturing process of the gate wiring. The manufacturing process ofan active matrix substrate of Embodiment 3 will be explained withreferences to FIGS. 17A to 19C. In this Embodiment, a method ofsimultaneously manufacturing a pixel TFT and a storage capacitor of apixel portion, and a TFT of a driver circuit provided in the peripheryof the pixel portion will be described in detail in accordance with theprocess. FIGS. 21A to 21F are diagrams showing a manufacturing method ofthe connecting wiring.

In FIG. 17A, a base film 602 formed from an insulating film made of asilicon oxide film, a silicon nitride film, or a silicon nitride oxidefilm, is formed on the surface of a glass substrate 601. In thisEmbodiment, the silicon nitride oxide film formed from SiH₄, NH₃, andN₂O at a thickness of between 10 and 200 nm, and a hydrogenated siliconnitride oxide film 602 formed from SiH₄ and N₂O at a thickness ofbetween 50 and 200 nm (preferably between 100 and 150 nm) on the surfaceof the silicon nitride oxide film, are formed in lamination by plasmaCVD.

An amorphous silicon film is next formed at a thickness of 55 nm byplasma CVD, and similar to Embodiment 1, is crystallized to thereby forma crystalline silicon film. Using a photomask PM11, a resist pattern isformed on the crystalline silicon film by a photolithography technique.A crystalline semiconductor film is divided into island shapes by dryetching to form island-like semiconductor films 604 to 608. A gaseousmixture of CF₄ and O₂ is used in the dry etching of the crystallinesilicon film. Then a gate insulating film 609 is formed from the siliconnitride oxide film at a film thickness of 120 nm by plasma CVD.

Subsequently, in order to form the gate wiring on the gate insulatingfilm 609, a heat-resistant conductive film is formed from a laminationfilm of metallic films 611 and 612 and a transparent conductive film613. The metallic film 611 is formed of a WN film, the metallic film 612is formed of a W film, and the transparent conductive film 613 is formedof an indium oxide zinc oxide alloy (In₂O₃—ZnO). (See FIGS. 17A and 21A)

Utilizing a second photo mask PM12, resist masks RM21 to RM27 are formedby using a photolithography technique. The transparent conductive film613 is etched to font gate wirings 618 to 622 and a storage capacitor623, and uppermost layers 618 a to 623 a and 683 a of a connectingwiring 683. (See FIGS. 17B and 21B)

As shown in FIGS. 18B and 21B, a side surface of the uppermost layers618 a to 623 a and 683 a, formed of the transparent conductive film, isetched further back than the resist masks RM21 to RM27. Next, themetallic films 611 and 613 are etched together to thereby complete thegate wirings 618 to 622 having taper shaped sectional surfaces, thecapacitor wiring 623, and the connecting wiring 683. (See FIGS. 17C and21C)

The wirings 618 to 623 and 683 become a laminated structure consistingof the uppermost layers 618 a to 623 a and 683 a formed of thetransparent conductive film 613, layers 618 b to 623 b and 683 b formedof the metallic film 612, and layers 618 c to 623 c and 683 c formed ofthe metallic film 611.

At this point, etching is performed such that a taper portion is formedat least in the edge portion of the gate wirings 618 to 622. Thisetching process is carried out with the ICP etching device. Etching isperformed under the following conditions: a gaseous mixture of CF₄ andCl₂ is used as the etching gas with the quantity of flow set to 30 SCCM,respectively; discharge power is set to 3.2 W/cm² (13.56 MHZ); biaspower is set to 244 mW/cm² (13.56 MHZ); and pressure is set to 1.0 Pa.Due to such etching conditions, in the edge portion of the gate wirings618 to 622, a taper portion with a gradual increase in thickness fromthe edge portion inward, informed with an angle of between 25° and 35°,preferably 30°. The angle of the taper portion will greatly influence ona concentration incline of a low-concentration n-type impurity region,which afterwards will form an LDD region. Note that an angle θ1 of thetaper portion is expressed by Tan(θ1)=HG/WG using the length (WG) andthe thickness (HG) of the taper portion.

In addition, in order to perform etching without leaving any residue,over-etching is performed approximately between 10% and 20% to thethickness of the insulating film 609. However, it is necessary to payattention to the selective ratio of etching to a base film at thispoint. For example, as shown in table 1, the selective ratio of the Wfilm to the silicon nitride oxide film (the gate insulating film 609) isbetween 2 and 4 (typically 3). Due to this type of over-etchingtreatment, an exposed surface of the silicon nitride oxide film isetched between 20 and 50 nm, becoming substantially thinner to therebyform a new shape gate insulating film 610.

The process of doping an impurity element that imparts n-type (n⁻ dopeprocess) is performed with the purpose of forming an LDD region of ann-channel TFT of the driver circuit and the pixel TFT. Resist masks 112to 117 used for the formation of the gate electrode are kept intact, andusing the gate wirings 618 to 622 having the taper portion in the edgeportion as masks, phosphorous as the impurity element that impartsn-type is doped by ion doping in a self-aligning manner (FIG. 18A)

Here in this process, in order to dope the impurity element that impartsn-type so that it passes through the taper portion of the wirings 618 to623 and [through] the gate insulating film 610 reaching thesemiconductor film positioned underneath, the acceleration voltage isset high, between 80 and 160 keV, and the dose quantity is set low,between 1×10¹³ and 5×10¹⁴ atoms/cm³ for the purpose of forming an LDDregion. The concentration of the impurity element to be doped into thesemiconductor film is doped in the concentration range of between 1×10¹⁶and 1×10¹⁹ atoms/cm³. Low-concentration n-type impurity regions 624 to629 are thus formed in the island-like semiconductor film as shown inFIG. 18A.

In this process, in the low-concentration n-type impurity regions 624 to628, at least the concentration inclination of phosphorous that isincluded in the portions that are overlapped with the gate wirings 618to 622 reflects the change in film thickness of the taper portion of thegate wiring 618 to 622. In other words, in the region overlapping thegate wiring, low-concentration n-type impurity regions 624 to 628gradually becomes higher towards the side surface of the gate wiring.This is because of the concentration change of phosphorous that hasreached the semiconductor film due to the difference in the filmthickness of the taper portion. Note that FIG. 18A is a diagram showinga perspective view of the low-concentration n-type impurity regions 624to 628. However, this diagram is not exactly a view showing the regionsdoped with phosphorous, but rather a view showing the above change inconcentration of phosphorous occurring in accordance with the shape ofthe taper portion of the gate wirings 618 to 622.

The formation of high-concentration n-type impurity regions forfunctioning as a source region or a drain region in the n channel TFTare performed next (n⁺ dope process). Leaving the resist masks RM21 toRM26 intact, phosphorous is doped by the ion doping method under thecondition of a low acceleration voltage of between 10 and 30 keV so thatthis time the gate wiring 618 to 622 functions as masks to shieldphosphorous. The high-concentration n-type impurity regions 630 to 635are thus formed. Since the gate insulating film 610 for covering theseregions 630 to 635 has been treated with over-etching in the processforming the gate wiring, the film thickness of the gate insulating filmhas become thinner to between 70 and 100 nm compared with the initialthickness of 120 nm. Accordingly, phosphorous can be doped appropriatelyeven under such a condition as low acceleration voltage. Theconcentration of phosphorous of these regions 630 to 635 is set to be inthe concentration range of between 1×10²⁰ and 1×10²¹ atoms/cm³. (SeeFIG. 18B)

High-concentration p-type impurity regions 636 and 637 as the sourceregion and the drain region are formed in the island-hie semiconductorfilms, 604 and 606 for forming the p channel TFT. Using the gate wirings618 and 120 as masks here, an impurity element that imparts p-type isdoped to thereby form the high-concentration p-type impurity regions 636and 637 in a self-aligning manner. At this point, the island-likesemiconductor films 605, 107, and 108 for forming the n-channel 141 arecovered entirely with resist masks RM29 through RM31 formed by using thethird photo mask PM23. (See FIG. 18C)

The impurity regions 636 and 637 to be formed here are formed by meansof ion doping using diborane (B₂H₆). The boron (B) concentration in thehigh-concentration p-type impurity regions that are not overlapped withthe gate wiring is set to be between 3×10²⁰ and 3×10²¹ atoms/cm³. Inaddition, because an impurity element is also doped into the impurityregion that are overlapped with the gate wiring via the gate insulatingfilm and the taper portion of the gate electrode, the region is formedas a substantially low-concentration p-type impurity region with theconcentration set to at least 1.5×10¹⁹ atoms/cm³ or more. Theconcentration of boron (B) is set to be 13 to 3 times that ofphosphorous doped in the process of FIG. 18A. Accordingly, no problem ofany kind will occur for the p-type impurity regions to function as thesource region and the drain region of the p-channel TFT.

Thereafter, a protecting insulating film 638 made of oxidized siliconnitride is formed as shown in FIGS. 19A and 21D. The silicon nitrideoxide film is formed from SiH₄, N₂O, and NH₃ by plasma CVD. The processof activating the impurity elements imparting the n-type or p-type thathas been doped at respective concentrations is performed by means ofthermal annealing using the annealing furnace.

Following the activation process, heat treatment is performed at between300 and 450. C for 1 to 12 hours in an atmosphere in which theatmosphere gas has been changed to contain 3% to 100% of hydrogen, andthen the hydrogenation process for the island-hie semiconductor film iscarried out. This process is to terminate the 10¹⁶ to 10¹⁸/cm³ ofdangling bonds in the island-hie semiconductor film by the thermallyexcited hydrogen.

After the completion of the activation and the hydrogenation processes,an interlayer insulating film 639 is formed so that an average filmthickness thereof falls between 1.0 and 2.0 mm. (See FIGS. 19B and 21E)

Thereafter, a resist mask of a predetermined pattern is formed using afourth photomask PM24, and a contact hole that reaches the source regionor the drain region formed in the respective island-like semiconductorfilms, and a protecting film 673 for covering the side surface ofconnecting wiring 683 is formed as shown in FIG. 21E.

This process is performed by means of dry etching. In this case, firstthe interlayer insulating film 639 made from an organic resin materialis etched using a gaseous mixture of CF₄, O₂, and He as etching gas, andthen the protecting insulating film 638 is etched with CF₄ and O₂ asetching gas. Furthermore, in order to raise the selective ratio to theisland-like semiconductor film, the etching gas is changed to CHF₃ toetch the gate insulating film 610 whereby a contact hole can be nicelyformed.

As shown in FIG. 21E, because the side surface of the connecting wiring683 is covered with the protecting film 673, the surface of the layers683 b and 683; formed from the metallic film of the connecting wiring683, is in a state surrounded by and in contact with the layer 683 aformed from the transparent conductive film, the gate insulating film610, and the protecting film 673. Therefore, the surface of the layers683 a and 683 b will not be exposed to air.

Then the metallic film formed of a lamination film of the Ti film(between 50 and 150 nm)/the Al film (between 300 and 400 nm) and thetransparent conductive film are formed, with the transparent conductivefilm formed on the surface of the metallic film at a thickness ofbetween 80 and 120 nm. As shown in FIG. 19C, the metallic film is formedby sputtering or vacuum evaporation, a resist mask pattern is formed byusing a fifth photomask PM25, and the metallic film and the transparentconductive film are etched to thereby form source wirings 648 to 652 anddrain wirings 653 to 657. The drain wiring 657 here is for functioningas the pixel electrode. The drain wiring 658 indicates the pixelelectrode of a neighboring pixel.

In a first p-channel TFT 700 of the driver circuit, a channel formingregion 706, a source region 707 and a drain region 708 formed from thehigh-concentration p-type impurity region are formed in the island-likesemiconductor film 604. In the regions 707 and 708, the region that areoverlapped with the gate electrode has become an LDD region with a lowconcentration of boron.

In a first n-channel TFT 701, the island-like semiconductor film 605 iscomposed of a channel forming region 709, LDD regions 710 and 711 formedfrom the low-concentration n-type impurity region and overlapped withthe gate wiring, and a source region 713 and a drain region 712 formedfrom the high-concentration n-type impurity region.

The concentration distribution of phosphorous in this LDD regionincreases as it becomes far from the channel forming region 709. Theproportion of increase differs depending on conditions such as theacceleration voltage and the dose quantity of ion doping, the taperangle and the thickness of the gate wiring 619. With the edge portion ofthe gate electrode formed into a taper shape, the impurity element canbe doped through the taper portion. Accordingly, an impurity region inwhich the concentration of the impurity element gradually changes can beformed in the semiconductor film existing underneath the taper portion.The present invention actively utilizes the impurity region describedabove. By forming this type of LDD region in the n-channel in, the highelectric field that generates in the vicinity of the drain region can berelaxed to thereby prevent the generation of a hot carrier, andprevention of the TFT from deteriorating can be realized.

Similar to the TFT 700, a second p-channel TFT 702 of the driver circuithas a channel forming region 714, and a source region 715 and a drainregion 716 formed from the high-concentration p-type impurity region inthe island-like semiconductor film 606. In the regions 715 and 716, theregion that are overlapped with the gate wiring has become a p-type LDDwith region h a low concentration of boron.

In a second n-channel TFT 703, the island-like semiconductor film 607has a channel forming regions 717, LDD regions 718 and 719 areoverlapped with a gate electrode 621, and a source region 720 and adrain region 721 formed from the high-concentration n-type impurityregion. The LDD regions 718 and 719 are structured similarly to the LDDregions 711 and 712.

In the pixel TFT 704, the island-like semiconductor film 608 has achannel forming regions 723 and 724, LDD regions 725 to 728 formed fromthe low-concentration n-type impurity region, and source or drainregions 729 to 731 formed from the high-concentration n-type impurityregion. The LDD regions 725 to 728 are structured similarly to the LDDregions 711 and 712.

In addition, in the storage capacitor 705, a channel forming region 732,LDD regions 733 and 734, and a high-concentration n-type impurity region735 in the semiconductor film 608 are revised so that the gateinsulating film 610 becomes a dielectric, and the storage capacitor 623and the semiconductor film 608 become electrodes.

Subsequently, similar to Embodiment 1, a column-shape spacer 672 formaintaining the space between substrates is formed using a sixthphotomask, and an opposing film 674 is formed to thereby performrubbing. Similarly to Embodiment 1, the opposing substrate 250 and theactive matrix substrate 700 are stuck together by a sealing agent 686with a liquid crystal material 260 enclosed in the gap between thesubstrate. The structure of the opposing substrate 250 is the same asthat of FIG. 8.

In addition, in the terminal portion of the connecting wiring 683, theFPC 191 is electrically connected thereto by the anisotropic conductivefilm 195 in which conductive grains 195 b are dispersed to an adhesive195 a as shown in FIG. 21F. In the FPC 191, reference numeral 191 adenotes a substrate made of a material such as polyimide and referencenumeral 191 b denotes a wiring made of copper etc.

Though a top gate TFT has been shown in Embodiments 1 through 3, aperson skilled in the art can readily replace this with a bottom gateTFT. Further, the active matrix substrate has been described in theseembodiments, and needless to say, the structure of the connecting wiringof these embodiments is applicable to other semiconductor devices. Forthe case of forming the protecting film of the connecting wiring fromthe interlayer insulating film of the TFT as in Embodiments 2 and 3, itis applicable to a semiconductor device having a circuit formed of thesuch as an active matrix type EL device.

Embodiment 4

The active matrix substrate, the liquid crystal display device and theEL display device fabricated in accordance with the present inventioncan be used for various electro-optical devices. The present inventioncan be applied to all those electronic appliances that include such anelectro-optical device as the display medium. Examples of the electronicappliances include a personal computer, a digital camera, a videocamera, a portable information terminal (a mobile computer, a cellulartelephone, an electronic book or the like), and a navigation system.FIG. 23A to 23F show examples of these.

FIG. 23A shows a personal computer, which comprises: a main body 2001incorporating a microprocessor and a memory, etc.; an image inputsection 2002; a display device 2003; and a keyboard 2004. The presentinvention can form the display device 2003 or other signal processingcircuits.

FIG. 23B shows a video camera, which comprises: a main body 2101; adisplay device 2102; a sound input section 2103; an operation switch2104; a battery 2105; and an image receiving section 2106. The presentinvention can be applied to the display device 2102 or other signalcontrol circuits.

FIG. 23C shows the portable information terminal, that comprises: a mainbody 2201; an image input section 2202; an image receiving section 2203;an operation switch 2204; and a display device 2205. The presentinvention can be applied to the display device 2205 or other signalcontrolling circuits.

Such a portable information terminal is often used outdoors as well asindoors. To operate the terminal for a long time, a reflection typeliquid crystal display device utilizing external light is more suitablefor the low power consumption type than the type using back-light.However, when the environment is dark, a transmission type liquidcrystal display device equipped with back-light is more suitable. Undersuch circumstances, a hybrid type liquid crystal display device havingthe features of both reflection type and transmission type has beendeveloped. The present invention can be also applied to such a hybridtype liquid crystal display device.

FIG. 22 shows an example of applying a liquid crystal panel ofEmbodiment 1 to a portable information terminal. The display device 2205comprises a touch panel 3002, a liquid crystal display device 3003 andLED back-light 3004. The touch panel 3002 is provided so as to easilyoperate the portable information terminal. Alight emitting element 3100such as LED is disposed at one of the ends of the touch panel 3002 and alight receiving device 3200 such as a photo-diode is disposed at theother end. An optical path is defined between them. When the touch panel3002 is pushed and the optical path is cut off, the output of the lightreceiving element 3200 changes. When these light emitting elements andlight receiving elements are disposed in matrix on the liquid crystaldisplay device by utilizing this principle, the touch panel can beallowed to function as the input medium.

FIG. 23D shows an electronic game machine such as a television game or avideo game. It comprises a main body 2301 having mounted thereto anelectronic circuit 2308 such as a CPU, a recording medium 2304, etc.; acontroller 2305; a display device 2303; and a display device 2302 thatis assembled in the main body 2301. The display device 2303 and thedisplay device 2302 assembled in the main body 2301 may display the sameinformation. Alternatively, the former may be used mainly as a maindisplay device and the latter, as a sub-display device to display theinformation of the recording medium 2304, the operation condition of theapparatus or as an operation board by adding the function of a touchsensor. The main body 2301, the controller 2305 and the display device2303 may have wire communication functions to transmit signals betweenthem, or may be equipped with sensor units 2306 and 2307 for achievingwireless communication or optical communication function. The presentinvention can be applied to the display devices 2302 and 2303. Aconventional CRT may be used for the display device 2303.

FIG. 23E shows a player that uses a recording medium storing a program(hereinafter called the “recording medium”). It comprises a main body2401, a display device 2402, a speaker unit 2403, a recording medium2404 and an operation switch 2405. Incidentally, a DVD (DigitalVersatile Disc) or a compact disk (CD) can be used for the recordingmedium to reproduce a music program or to display images or informationdisplay such as a video game (or a television game) and informationdisplay through the Internet. The present invention can be utilizedsuitably for the display device 2402 and other signal control circuits.

FIG. 23F shows a digital camera, which comprises: a main body 2501; adisplay device 2502; a view finder section 2503; an operation switch2504; and an image reception unit (not shown). The present invention canbe applied to the display unit 2502 or other signal control circuits.

FIG. 24A shows a front type projector, which comprises: a light sourceoptical system and a display device 2601; and a screen 2602. The presentinvention can be applied to the display device and other signal controlcircuits. FIG. 24B shows a rear type projector, which comprises: a mainbody 2701; a light source optical system and a display device 2702; amirror 2703; and a screen 2704. The present invention can be applied tothe display device or other signal control circuit.

Incidentally, FIG. 24C shows an example of the construction of the lightsource optical system and the display devices 2601 and 2702 in FIGS. 24Aand 24B. The light source optical system and the display device 2601 and2702 comprise a light source optical system 2801, mirrors 2802, 2804 to2806, a dichroic mirror 2803, a beam splitter 2807, a liquid crystaldisplay device 2808, a phase difference plate 2809 and a projectionoptical system 2810. The projection optical system 2810 comprises aplurality of optical lenses.

FIG. 24C shows an example of the three-plate system that uses threeliquid crystal display devices 2808. However, the present invention isnot limited to such a system, but may be applied to a single-plateoptical system. Optical lenses, a film having a polarization function, afilm for adjusting the phase, an IR film, etc, may be insertedappropriately in the optical path indicated by an arrow in FIG. 24C.FIG. 24D shows a structural example of the light source optical system2801 in FIG. 24C. In this embodiment, the light source optical system2801 comprises: a reflector 2811; a light source 2812; lens arrays 2813and 2814; a polarization conversion element 2815; and a convergent lens2816. Incidentally, the light source optical system shown in FIG. 24D isan example but is in no way restrictive.

The present invention can be further applied to a read circuit of anavigation system or an image sensor, though they are not shown in thedrawings. The application range of the present invention is thusextremely broad, and the present invention can be applied to electronicappliances of all fields.

By implementing the present invention, in the connecting wiringconnected to another circuit by means of the anisotropic conductivefilm, the connecting wiring becomes a structure in which the metallicfilm is covered with the protecting film and the transparent conductivefilm. Accordingly, corrosion and change in quality of the metallic filmcaused by manufacturing processes and contact with the adhesives of theanisotropic conductive film can be prevented to thereby form a contactstructure high in reliability.

1. A display device comprising: a substrate; a transistor over thesubstrate; a connecting wiring over the substrate, the connecting wiringbeing made of a same layer as a source wiring or a drain wiring of thetransistor; and an anisotropic conductive film in direct contact withthe connecting wiring, wherein the connecting wiring comprises ametallic film and a transparent conductive film formed over the metallicfilm, and wherein a side surface of the metallic film is covered and indirect contact with a protecting film.
 2. A display device according toclaim 1, further comprising a columnar spacer formed over the substrate,wherein the protecting film is formed of a same film as the columnarspacer.
 3. A display device comprising: a substrate; a transistor overthe substrate; a connecting wiring over the substrate, the connectingwiring being made of a same layer as a gate wiring of the transistor;and an anisotropic conductive film in direct contact with the connectingwiring, wherein the connecting wiring comprises a metallic film and atransparent conductive film formed over the metallic film, and wherein aside surface of the metallic film is covered and in direct contact witha protecting film.
 4. A display device according to claim 3, furthercomprising an insulating film interposed between the gate wiring and asource wiring or a drain wiring of the transistor, wherein theprotecting film is formed of a same film as the insulating film.
 5. Thedisplay device according to claim 1, wherein the transparent conductivefilm contains indium oxide or zinc oxide.
 6. The display deviceaccording to claim 3, wherein the transparent conductive film containsindium oxide or zinc oxide.
 7. The display device according to claim 3,wherein the metallic film comprises a metallic layer having Al or W asits main constituent, or an alloy containing one or both of Al and W. 8.The display device according to claim 1, wherein the protecting filmcomprises a resin film.
 9. The display device according to claim 3,wherein the protecting film comprises a resin film.
 10. The displaydevice according to claim 1, wherein the metallic film comprises ametallic layer having Al or W as its main constituent, or an alloycontaining one or both of Al and W.
 11. The display device according toclaim 3, wherein the metallic film comprises a metallic layer having Alor W as its main constituent, or an alloy containing one or both of Aland W.
 12. The display device according to claim 1, further comprising afacing substrate and a corresponding wiring on the other substrate,wherein the connecting wiring of the substrate is electrically connectedto the corresponding wiring of the facing substrate via the anisotropicconductive film.
 13. The display device according to claim 3, furthercomprising a facing substrate and a corresponding wiring on the othersubstrate, wherein the connecting wiring of the substrate iselectrically connected to the corresponding wiring of the facingsubstrate via the anisotropic conductive film.
 14. The display deviceaccording to claim 1, wherein said display device is one of a liquidcrystal display device and EL display device.
 15. The display deviceaccording to claim 3, wherein said display device is one of a liquidcrystal display device and EL display device.
 16. A display devicecomprising: a substrate; a connecting wiring over the substrate, theconnecting wiring comprising: a metallic film; and a transparentconductive film on and in contact with the metallic film; an organicinsulating film thicker than the connecting wiring, in direct contactwith a side surface of the metallic film and over a peripheral portionof the metallic film; and an anisotropic conductive film on and indirect contact with the transparent conductive film.
 17. A displaydevice comprising: a substrate; a connecting wiring over the substrate,the connecting wiring comprising: a metallic film; and a transparentconductive film on and in contact with the metallic film; an inorganicinsulating film having a portion in direct contact with a side surfaceof the metallic film; an organic insulating film thicker than theconnecting wiring and covering the portion of the inorganic insulatingfilm; and an anisotropic conductive film on and in direct contact withthe transparent conductive film.
 18. A display device according to claim17, further comprising: a transistor on the substrate; a protectinginsulating film over the transistor; an interlayer insulating film overthe protecting insulating film; a wiring over the interlayer insulatingfilm electrically connected to a source or a drain of the transistorthrough the interlayer insulating film and the protecting insulatingfilm, wherein the protecting insulating film and the inorganicinsulating film are made from a same material.
 19. A display deviceaccording to claim 17, further comprising: a transistor on thesubstrate; a protecting insulating film over the transistor; aninterlayer insulating film over the protecting insulating film; a wiringover the interlayer insulating film electrically connected to a sourceor a drain of the transistor through the interlayer insulating film andthe protecting insulating film, wherein the protecting insulating filmand the inorganic insulating film are made from a same layer.
 20. Adisplay device according to claim 17, wherein the anisotropic conductivefilm is in contact with a side portion of the inorganic insulating film.21. A display device comprising: a substrate; a connecting wiring overthe substrate, the connecting wiring comprising: a metallic film; and atransparent conductive film on and in contact with the metallic film; aninsulating film thicker than the connecting wiring, in direct contactwith a side surface of the metallic film and over a peripheral portionof the metallic film; an anisotropic conductive film on and in directcontact with the transparent conductive film; a flexible printed circuiton the anisotropic conductive film; and a polymer layer at an edgeportion of the flexible printed circuit so as to fix the flexibleprinted circuit to the substrate.
 22. A display device according toclaim 21, wherein the polymer layer is a resin layer
 23. A displaydevice comprising: a substrate; a pixel over the substrate, the pixelcomprising: a transistor; an insulating layer over the transistor; and awiring over the insulating layer electrically connected to a source or adrain of the transistor through the insulating layer; an opposingsubstrate facing the substrate over the pixel; a columnar spacer formedover the wiring and configured to hold a distance between the substrateand the opposing substrate; a connecting wiring over the substrate, theconnecting wiring comprising: a metallic film; and a transparentconductive film on and in contact with the metallic film; an insulatingfilm thicker than the connecting wiring, in direct contact with a sidesurface of the metallic film and over a peripheral portion of themetallic film; and an anisotropic conductive film on and in directcontact with the transparent conductive film.
 24. A display deviceaccording to claim 23, wherein the columnar spacer and the insulatingfilm are made from a same material.
 25. A display device according toclaim 23, wherein the columnar spacer and the insulating film are madefrom a same layer.
 26. A display device according to claim 23, furthercomprising a shielding film formed on the opposing substrate andoverlapping the transistor.
 27. A display device comprising: asubstrate; a transistor over the substrate; an opposing substrate facingthe substrate over the transistor; a shielding film formed on theopposing substrate and overlapping the transistor; a connecting wiringover the substrate, the connecting wiring comprising: a metallic film;and a transparent conductive film on and in contact with the metallicfilm; an insulating film thicker than the connecting wiring, in directcontact with a side surface of the metallic film and over a peripheralportion of the metallic film; and an anisotropic conductive film on andin direct contact with the transparent conductive film.
 28. A displaydevice comprising: a substrate; a transistor over the substrate; anopposing substrate facing the substrate over the transistor; a shieldingfilm and a color filter formed on the opposing substrate, the shieldingfilm overlapping the transistor; a connecting wiring over the substrate,the connecting wiring comprising: a metallic film; and a transparentconductive film on and in contact with the metallic film; an insulatingfilm thicker than the connecting wiring, in direct contact with a sidesurface of the metallic film and over a peripheral portion of themetallic film; and an anisotropic conductive film on and in directcontact with the transparent conductive film.
 29. A display deviceaccording to claim 26, wherein the shielding film comprises aluminum,chromium, or titanium.
 30. A display device according to claim 27,wherein the shielding film comprises aluminum, chromium, or titanium.31. A display device according to claim 28, wherein the shielding filmcomprises aluminum, chromium, or titanium.
 32. A display deviceaccording to claim 26, wherein the shielding film is able to blocklight.
 33. A display device according to claim 27, wherein the shieldingfilm is able to block light.
 34. A display device according to claim 28,wherein the shielding film is able to block light.
 35. A display deviceaccording to claim 16, wherein the transparent conductive film and theorganic insulating film prevent the connecting wiring from being exposedto air or in contact with the anisotropic conductive film.
 36. A displaydevice according to claim 17, wherein the transparent conductive film,the organic insulating film and the inorganic insulating film preventthe connecting wiring from being exposed to air or in contact with theanisotropic conductive film.
 37. A display device according to claim 21,wherein the transparent conductive film and the insulating film preventthe connecting wiring from being exposed to air or in contact with theanisotropic conductive film.
 38. A display device according to claim 23,wherein the transparent conductive film and the insulating film preventthe connecting wiring from being exposed to air or in contact with theanisotropic conductive film.
 39. A display device according to claim 27,wherein the transparent conductive film and the insulating film preventthe connecting wiring from being exposed to air or in contact with theanisotropic conductive film.
 40. A display device according to claim 28,wherein the transparent conductive film and the insulating film preventthe connecting wiring from being exposed to air or in contact with theanisotropic conductive film.
 41. A display device according to claim 16,wherein the transparent conductive film is formed on a whole top surfaceof the metallic film.
 42. A display device according to claim 17,wherein the transparent conductive film is formed on a whole top surfaceof the metallic film.
 43. A display device according to claim 21,wherein the transparent conductive film is formed on a whole top surfaceof the metallic film.
 44. A display device according to claim 23,wherein the transparent conductive film is formed on a whole top surfaceof the metallic film.
 45. A display device according to claim 27,wherein the transparent conductive film is formed on a whole top surfaceof the metallic film.
 46. A display device according to claim 28,wherein the transparent conductive film is formed on a whole top surfaceof the metallic film.
 47. A display device according to claim 16,wherein the organic insulating film is non-conformal.
 48. A displaydevice according to claim 17, wherein the organic insulating film isnon-conformal.
 49. A display device according to claim 21, wherein theinsulating film is non-conformal.
 50. A display device according toclaim 23, wherein the insulating film is non-conformal.
 51. A displaydevice according to claim 27, wherein the insulating film isnon-conformal.
 52. A display device according to claim 28, wherein theinsulating film is non-conformal.
 53. A display device according toclaim 21, wherein the insulating film comprises an organic material. 54.A display device according to claim 23, wherein the insulating filmcomprises an organic material.
 55. A display device according to claim27, wherein the insulating film comprises an organic material.
 56. Adisplay device according to claim 28, wherein the insulating filmcomprises an organic material.